Detailed airborne magnetic surveys have been useful in exploring overthrusts containing magnetic, igneous rocks. The structural configuration of these rocks can be closely approximated. The most important information is the thickness of igneous material overlying sediments and the dip of the overthrust base. Thicknesses and dips of magnetic rocks in overthrusts can be highly variable. Thickness variations of 20,000 ft have been found to occur over the course of 5 mi parallel with the toe of the thrust. The igneous to sedimentary rock contact can range from vertical to horizontal in the same distance.

Interpretations can be used to guide the exploration program in overthrust areas. Seismic surveys can be located in areas of thin granite cover so prospective structures in the underlying sediments might be located at shallower depths.

The Arbuckle Mountain Range is an example of an overthrust that can be explored in this fashion. This overthrust covers a large surface area; in places it is very thin and in others, very thick, being in contact with the basement. The thrust covers a large surface area in an intensely drilled basin. The sediments below the thrust cover an area large enough to "hide" several major oil fields.

Undrilled areas large enough to contain major oil reserves are becoming increasingly scarce. The use of magnetics to detect and map igneous overthrusts can find undrilled sedimentary areas large enough to contain major reserve prospects.

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